Our general aim is to define the mechanism governing the expression of cell surface proteins involved in transmembrane signalling. Using cultured embryonic muscle cells, we are studying the regulation of topologic distribution, metabolic stability, and biochemical properties of the Acetylcholine Receptor (AChR), a well-characterized muscle membrane glycoprotein mediating neuromuscular transmission. We will investigate the roles of AChR (1) synthesis; (2) glycosylation; and (3) interaction with muscle cytoskeleton in control of AChR expression and the effects of neuronal influence on these processes. Fluorescent, and radioactive derivatives of alpha bungarotoxin, an AChR-specific polypeptide ligand, will be used to monitor changes in receptor properties associated with differentiation and neuronal intervention. Biosynthesis will be studied by purification of newly-synthesized AChR by affinity chromotography and characterization by electrophoretic methods. The functional significance of carbohydrate moieties of AChR will be investigated using lectins and tunicamycin, an inhibitor of protein glycosylation. To study the role of the cytoskeletal framework in organization and aggregation of muscle cell surface AChR, we will utilize staining techniques that allow simultaneous visualization of surface receptor and specific proteins of the cytoskeleton or basal lamina. A detergent extraction procedure that selectively removes membrane lipids and soluble proteins while preserving the cytoskeleton with attached cell surface proteins will be utilized to study the transmembrane interactions of AChR. The objective is to test the hypothesis that the surface distribution of AChR is controlled by specific interactions with structural proteins at the cell periphery.